In radio communications, there has been a problem that efficiency of frequency usage lowers at a cell edge. Therefore, the IMT-Advanced (4th-generation mobile communications system) and others are studying a method that deals with this problem by performing link control on a plurality of base stations.
However, when a radio terminal receives signals for a plurality of link-controlled radio base stations, distances between the radio terminal and the respective radio base stations are different from each other. Therefore, differences occur in signal reception timing according to which the radio terminal receives the signals from the plurality of link-controlled radio base stations. Also, the signals transmitted from the plurality of link-controlled radio base stations are the signals produced by the different radio base stations so that there are differences in frequency offset.
Accordingly, instead of performing the link-control on completely different radio base stations, such a method has been proposed that separates RRHs that are radio parts from the same radio base station, and disperses them in a plurality of locations, respectively (e.g., see PTL 1 (National Publication No. 2008-506321).
According to this method, signals transmitted from the plurality of RRHs are produced by the same radio base station so that no difference occurs in frequency offset between the signals received from the plurality of RRHs.